1. Technical Field
The present invention relates to a system for processing food items to form slices. More specifically, this invention relates to hydraulically transporting food items with the use of an eductor, reducing the size of large items using a segmented cutter, maximizing cutting efficiency by controlling velocities and mass flow rates, slicing food items with a transverse slicer, controlling slicing velocities to optimize performance, and controllably spreading the resulting slices upon a conveyor for further processing.
2. Description of Related Art
The commercial process of processing produce such as vegetables, tubers, nuts, and fruit requires sized reduction of large volumes of food stuffs. The present invention will be described in terms of transporting and slicing potatoes to make potato chips. However, as those skilled in the art will appreciate, the present invention can be employed for a wide variety of uses other than making potato chips.
Prior art industrial-sized potato slicing systems typically use centrifugal slicers to cut potatoes into slices, which can be used to make products such as potato chips, or dishes such as scalloped potatoes and au gratin potatoes. A centrifugal slicer, such as the Urschel Model Continuous Cut (“CC”) Slicer, manufactured by Urschel Laboratories, Inc., comprises several upright blades arranged in a ring around a central impeller or rotary disk. FIG. 6 of U.S. Pat. No. 5,694,824, granted to Jacko et al., for example, shows one such prior art centrifugal slicer. As potatoes are fed into the slicer, the rotating impeller or disk initially throws potatoes against the blades and then pushes the potatoes across the blades, thereby shaving slices from the potatoes.
Centrifugal-type slicers, however, have several drawbacks. One such drawback is reduced yield due to high slicing velocities. In order for centrifugal slicers to work properly, a minimum amount of rotational speed is required to create the centrifugal force necessary to force the potatoes against the cutting surfaces. As a result of the relatively high slicing and impact speeds, centrifugal slicers (or cutters) generally produce a considerable amount of waste and scrap. For example, a potato can be damaged when it is thrown against the slicer walls between blades, as well as when a blade merely nicks the surface but fails to remove a slice. Furthermore, the high slicing speeds cause a significant amount of potato cell damage. A potato's starch-containing cells are viscoelastic, which means that the more quickly pressure is applied during slicing, the more brittle the cell walls become. Thus, the number of potato cells damaged per slice increases as the slicing speed increases. When potato cells break, the contained starch is released, resulting in reduced product yield. As much as 16% by weight of the potato feed can be lost to waste, scraps, and cell damage when using centrifugal slicers.
A second drawback of centrifugal-type slicers is the undesirable level of cracking that such slicers can impart in the slices. Because the viscoelastic potato cells become more brittle with increased blade impact speed, the slices become more likely to crack as the impact speed increases. Such cracking undesirably increases the occurrence of slice fold-overs and the amount of oil-uptake.
In addition, centrifugal slicers can only accommodate round chipping potatoes and cannot accommodate large elongated potatoes. Elongated potatoes tend to plug centrifugal slicers. Elongated potatoes also tend to lay sideways in such slicers, which undesirably increases variability in slice thickness. Moreover, centrifugal slicers create undesirably shaped, oblong potato chips when supplied with normal elongated potatoes. FIGS. 1a and 1b show examples of slices produced when a centrifugal slicer is supplied with a round potato 110 versus an elongated potato 140. A centrifugal slicer will slice a round chipping potato 110 into round slices with ridges 130 or without ridges 120, depending upon whether the slicer's blade edges are corrugated. In contrast, a centrifugal slicer will slice an elongated potato 140 lengthwise into oblong slices with or without ridges 160, 150, depending on whether the blade edges are corrugated. While some variation in slice or chip shape is acceptable, slices or chips having extreme aspect ratios (ratio of length to width) may be undesirable in some circumstances. Thus, elongated potatoes are generally not used in centrifugal slicers because of the potentially undesirable oblong-shaped slices they produce.
Although several non-centrifugal-type cutters exist for processing potatoes, few of them relate specifically to creating potato slices suitable for products such as potato chips. For example, U.S. Pat. Nos. 5,394,793, and 5,343,791, granted to Julian et. al., disclose rotating cutting head assemblies for cutting singular potatoes into helical strips. As the spiral cutting heads rotate, they make continuous helical bores through singular potatoes, thus making helical strips. The devices disclosed in the '793 and '791 patents, however, are not suitable for cutting potato slices.
A few potato slicer systems use horizontal discs with blades to slice potatoes. For example, U.S. Pat. No. 4,706,556, granted to Wallace et al., discloses a horizontal slicing disc with an inclined potato feeding tube. Wallace et al. teach that the potatoes must be individually removed from a washer drum and deposited into the slicer's feed tube. Prior to the current invention, however, there has been no automated slicing system for maximizing cutting efficiency and product yield. More specifically, there has been no automated system for controlling the feed rate of the potatoes to a transverse slicer and slicing the potatoes at an automatically controlled and reduced slicing speed.
Many prior-art slicing systems transport potatoes from one place to another by propelling them with an impeller-type food pump such as the Single Port Impeller Pump manufactured by the Cornell Pump Company. A significant number of the potatoes, however, are damaged as the potatoes travel through the pump and are struck by the rotating impeller. Furthermore, impeller-type food pumps draw a significant amount of energy and can therefore be expensive to operate. The cost of periodically replacing the impellers due to wear and tear also adds to the operating and maintenance costs. Other slicing systems, with the use of a venturi, accelerate a flow of solid food items and water through a set of stationary blades. For example, U.S. Pat. No. 5,390,590, granted to Mendenhall, discloses both concepts. Mendenhall discloses a hydraulic cutter in which a centrifugal food pump sends potatoes and water through a venturi tube, which in turn accelerates the potatoes through a grid of stationary blades. Slicing systems such as that disclosed in Mendenhall, however, relate to processes for making french fries and are not suitable for making potato chips or other products using potato slices. Prior to this invention, few potato slicing systems have used an eductor/venturi system to gently transport potatoes in a non-destructive manner throughout a process for making slices. Furthermore, no prior art slicing system has used a plurality of diverters to divide a stream of food items into several independently controlled streams, gently fed such food items into and propelled such streams through a manifold of several independently controlled eductors.
Prior art potato processing systems use potato halvers, such as Grove Dale Corporation's Auto Halver, to reduce the size of potatoes that are too large for processing. These potato halvers cut potatoes cross-wise along the short axis to reduce the overall length of oversized potatoes by half. Such halvers, however, are not suitable in potato slicing systems in which potatoes are cut into transverse slices, since such cutters do not reduce the diameter of potato pieces in the minor dimension.
Another problem encountered with prior art methods and devices is that the resulting potato slices often undesirably clump together as they exit the slicers and are moved downstream for further processing. Slice clumping prevents the slices from being evenly distributed upon a conveyor. Slice clumping also hinders the slices from being properly baked, toasted, or fried.
Resulting potato slices often contain slicing scraps, loose starch and other undesirable fines that are desirably removed from the slices before further processing. Prior art slicing systems typically remove loose starch, slicing scraps and fines by transporting slices to, and processing them through, a separate washing unit. Thus, there is a need for a simplified method for removing loose starch and slicing scraps.
Consequently, a need exists for a food processing system that can slice food items such as potatoes with less waste and scrap, as well as accommodate a wider variety of food shapes. More specifically, such a system should process potatoes with a relatively slower slicing speed and accommodate both round and oblong potatoes by slicing potatoes transversely. Such a system should also reduce oversized potatoes by slicing them lengthwise into smaller-diameter segments. The novel system should transport potatoes and potato segments in a flume of fluid towards at least one slicer with the use of an eductor/venturi system that gently propels potatoes in a non-destructive manner. Once cut, the system should transport the slices in a flume of fluid for further processing. Such a flume of fluid should also wash away loose starch, remove slicing scraps and remove undesirable fines from the slices. In addition, such a slicing system should prevent slice clumping and controllably distribute slices upon a conveyor leading to the next processing unit operation. Such a system should preferably be automated, but it should also be amenable to manual operation if desired.